Amplifier circuit having constant output swing range and stable delay time

ABSTRACT

Provided is an amplifier circuit having a constant output swing range and a stable delay time, where the amplifier circuit includes a first bias unit, a second bias unit, a comparison unit, and an amplifier unit, and the first bias unit responds to an internal reference signal with a predetermined voltage level and maintains constant the amount of a first current, and the second bias unit receives an external reference signal, responds to a control voltage, and controls the amount of a second current to be the same as the amount of the first current, and the comparison unit compares a voltage level of a first node with a voltage level of a second node, and controls a voltage level of the control voltage according to the comparison result, and the amplifier unit compares a voltage level of an external input signal with a voltage level of the external reference signal, amplifies and outputs a voltage difference between the two compared signals, responds to the control voltage, and controls the amount of a third current to be the same as the amount of the first current although the level of the external reference signal is varied, such that the amplifier circuit and a circuit for receiving data can maintain a constant output swing range and a stable delay time irrespective of variations in the voltage levels of the external input signal or the external reference signal.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims foreign priority under 35 U.S.C. § 119 to KoreanPatent Application No. 2004-14953, filed on Mar. 5, 2004, in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to amplifier circuits, and moreparticularly, to amplifier circuits that are robust to variations in avoltage level of an external reference signal or an external inputsignal.

2. Description of the Related Art

In the semiconductor device field, as data transmission speeds betweensemiconductor chips is increasing, power consumed in data interfaces isalso increasing.

In order to reduce power consumption, an attempt has been made to reducean operating voltage level. However, it is more difficult for a datareceiver to receive data when the operating voltage level is reduced,but noise in the interface is not reduced enough.

In particular, since the speed of the interface increases, the operatingvoltage level is reduced to prevent increasing power consumption, and atermination circuit is used to reduce noise between signals. Voltagelevels of whole signals are reduced, thereby reducing drastically aswing range of an external signal input to an amplifier circuit.

FIG. 1 is a diagram for explaining a reduction in a swing range of anexternal input signal and variations in a delay time, indicatedgenerally by the reference numeral 100. Referring to FIG. 1, a highlevel band VIHBAND in which the external input signal is recognized as ahigh level signal, and a low level band VILBAND in which the externalinput signal is recognized as a low level signal, are reduced graduallyto a point where the bands become narrower than a reference signal bandVREFBAND.

If the high level band VIHBAND and the low level band VILBAND arereduced and a level of a reference signal is varied within the referencesignal band VREFBAND, a valid window in which the external input signalcan be recognized as a high level signal or a low level signal isreduced disadvantageously.

FIG. 2 is a circuit diagram of a conventional amplifier circuit.Referring to FIG. 2, a conventional amplifier circuit 200 includes abias unit 210, which generates a bias voltage VBIAS having a constantvoltage level, and an amplifier unit 220, which responds to the biasvoltage VBIAS and outputs amplified data.

The bias unit 210 includes first through fourth transistors TR1, TR2,TR3, and TR4, respectively, which build a current mirror. Since a powervoltage VDD is applied to a gate of the third transistor TR3, the thirdtransistor TR3 is always turned on, and accordingly, a gate of the firsttransistor TR1 changes to a low level due to a ground voltage VSS.

Therefore, the first transistor TR1 and the second transistor TR2 areturned on, and a first node N1 maintains a constant voltage level due tocurrent flowing through the second transistor TR2. At this time, theamount of the current flowing through the second transistor TR2 can becontrolled and the voltage level of the first node N1 can also becontrolled by adjusting the size of the first transistor TR1 and thesecond transistor TR2. The voltage at the first node N1 makes the fourthtransistor TR4 turn on, and is output as the bias voltage VBIAS. Thebias voltage VBIAS output from the bias unit 210 is maintained constant.

The amplifier unit 220 includes fifth through ninth transistors TR5,TR6, TR7, TR8, and TR9, which amplify a voltage difference between anexternal reference signal XVREF and an external input signal XIN, andoutput, respectively, data DATA and inverted data DATAB through anoutput node OUTN and an inverted output node OUTNB.

The fifth transistor TR5 and the sixth transistor TR6 are turned on dueto the ground voltage VSS connected to gates thereof, and a degree towhich the seventh transistor TR7 and the eighth transistor TR8 areturned on is determined depending on voltage levels of the externalreference signal XVREF and the external input signal XIN, respectivelyinput to the fifth transistor TR5 and the sixth transistor TR6. Theninth transistor TR9 responds to the bias voltage VBIAS and determinesthe whole operation of the amplifier unit 220. That is, if the ninthtransistor TR9 is turned on, the amplifier unit 220 operates, and if theninth TR9 is turned off, the amplifier unit 220 does not operate. If thevoltage level of the bias voltage VBIAS applied to the ninth transistorTR9 is constant, swing ranges of the data DATA and the inverted dataDATAB output from the amplifier unit 220 are maintained constant.

The operation of the amplifier unit 220 is equal to that of a generaldifferential amplifier, which is well known to one of ordinary skill inthe pertinent art, and thus, a detailed explanation thereof will not begiven.

FIG. 3A shows a graph 300 illustrating the external input signal and theexternal reference signal input to the amplifier circuit shown in FIG.2. FIG. 3B shows a graph 350 illustrating the data output from theamplifier circuit shown in FIG. 2.

Referring to FIG. 3A, the voltage level of the external input signal XINand the external reference signal XVREF is not constant, but is varied.That is, as the level of the external input signal XIN is varied, thelevel of the external reference signal XVREF is also varied to 0.55V,0.75V, and 0.95V.

Accordingly, although the voltage level of the bias voltage VBIASapplied to the ninth transistor TR9 of the amplifier unit 220 isconstant, if the level of the external input signal XIN and the level ofthe external reference signal XVREF are varied as shown in FIG. 3A, theswing ranges of the data DATA and the inverted data DATAB output fromthe amplifier circuit 200 are not constant and output delay times areincreased.

This is because as the voltage levels of the external input signal XINand the external reference signal XVREF are varied, a voltage level of asecond node N2 of the amplifier unit 220 is varied. Referring to FIG.3B, it can be seen that the swing range of the data DATA is notconstant, as is shown by arrows (i), (ii), and (iii). Further, it can beseen that an output delay time TD taken from when data DATA is output towhen next data DATA is output is relatively long.

As a result, the conventional amplifier circuit has poor performance inthat when the voltage levels of the external input signal XIN and theexternal reference signal XVREF are varied, the output swing ranges arenot constant and the output delay times are increased.

SUMMARY OF THE INVENTION

The present disclosure provides an exemplary amplifier circuitembodiment, which maintains a constant output swing range and a stableoutput delay time irrespective of variations in voltage levels of anexternal input signal and an external reference signal.

The present disclosure also provides an exemplary data receiving circuitembodiment comprising an amplifier circuit that maintains a constantoutput swing range and a stable output delay time irrespective ofvariations in voltage levels of an external input signal and an externalreference signal.

According to an aspect of the present disclosure, there is provided anamplifier circuit comprising a first bias unit, a second bias unit, acomparison unit, and an amplifier unit. The first bias unit responds toan internal reference signal with a predetermined voltage level andmaintains constant the amount of a first current. The second bias unitreceives an external reference signal, responds to a control voltage,and controls the amount of a second current to be same as the amount ofthe first current.

The comparison unit compares a voltage level of a first node with avoltage level of a second node and controls a voltage level of thecontrol voltage according to the comparison result. The amplifier unitcompares a voltage level of an external input signal and a voltage levelof the external reference signal, amplifies and outputs a voltagedifference between the two compared signals, responds to the controlvoltage, and controls the amount of a third current to be same as theamount of the first current although the level of the external referencesignal is varied.

The first current may flow through the first node, the second currentmay flow through the second node, and the amount of the second currentmay be varied in response to the voltage level of the external referencesignal. The first bias unit may comprise first through third biastransistors. The first bias transistor may have a first terminalconnected to a power voltage, a gate connected to a ground voltage, anda second terminal connected to the first node. The second biastransistor may have a first terminal connected to the first node, and agate to which the internal reference signal is applied.

The third bias transistor may have a first terminal connected to asecond terminal of the second bias transistor, a gate to which theinternal reference signal is applied, and a second terminal connected tothe ground voltage. The internal reference signal may make the secondbias transistor and the third bias transistor turn on to maintainconstant the amount of the first current. The second bias unit maycomprise fourth through sixth bias transistors. The fourth biastransistor may have a first terminal connected to the power voltage, agate connected to the ground voltage, and a second terminal connected tothe second node. The fifth bias transistor may have a first terminalconnected to the second node, and a gate to which the external referencesignal is applied. The sixth bias transistor may have a first terminalconnected to a second terminal of the fifth bias transistor, a gate towhich the control voltage is applied, and a second terminal connected tothe ground voltage.

The control voltage may control a degree to which the sixth biastransistor is turned on and control the amount of the second current tobe the same as the amount of the first current. The comparison unit mayhave a negative terminal connected to the first node and a positiveterminal connected to the second node, and reduce the voltage level ofthe control voltage if the voltage level of the second node is higherthan the voltage level of the first node and increase the voltage levelof the control voltage if the voltage level of the second node is lowerthan the voltage level of the first node.

The amplifier unit may comprise first through fifth transistors. Thefirst transistor may have a first terminal connected to the powervoltage, a gate to which a ground voltage is connected, and a secondterminal connected to an output node. The second transistor may have afirst terminal connected to the output node, a gate to which theexternal reference signal is applied, and a second terminal connected toa third node.

The third transistor may have a first terminal connected to the powervoltage, a gate connected to the ground voltage, and a second terminalconnected to an inverted output node. The fourth transistor may have afirst terminal connected to the inverted output node, a gate to whichthe external input signal is applied, and a second terminal connected tothe third node. The fifth transistor may have a first terminal connectedto the third node, a gate to which the control voltage is applied, and asecond terminal connected to the ground voltage.

According to another aspect of the present disclosure, there is provideda circuit for receiving data comprising an amplifier circuit, aninternal latch circuit, and an external latch circuit. The amplifiercircuit compares a voltage level of an external input signal with avoltage level of an external reference signal, amplifies and outputs avoltage difference between the two compared signals, responds to acontrol voltage, and maintains constant a swing range of output data.

The internal latch circuit stores and amplifies the data output from theamplifier circuit. The external latch circuit stores or outwardlyoutputs the data output from the internal latch circuit.

The amplifier circuit may comprise a first bias unit, a second biasunit, a comparison unit, and an amplifier unit. The first bias unit mayrespond to an internal reference signal with a predetermined voltagelevel and maintain constant the amount of a first current. The secondbias unit may receive the external reference signal, respond to thecontrol voltage, and control the amount of a second current to be thesame as the amount of the first current. The comparison unit may comparea voltage level of a first node with a voltage level of a second node,and control a voltage level of the control voltage according to thecomparison result.

The amplifier unit may compare the voltage level of the external inputsignal with the voltage level of the external reference signal, amplifyand output the voltage difference between the two compared signals,respond to the control voltage, and maintain constant the swing range ofthe output data although the levels of the external reference signal andthe external input signal are varied. The amplifier circuit may beturned on or off in response to a predetermined amplifier circuitdriving pulse.

The internal latch circuit may comprise first through fourth internallatch transistors. The first internal latch transistor may have a firstterminal connected to a power voltage, a gate connected to an invertedoutput node of the amplifier circuit, and a second terminal connected toan output node of the amplifier circuit.

The second internal latch transistor may have a first terminal connectedto the power voltage, a gate connected to the output node of theamplifier circuit, and a second terminal connected to the invertedoutput node of the amplifier circuit. The third internal latchtransistor may have a first terminal connected to the output node, agate connected to the inverted output node, and a second terminalconnected to an internal latch node.

The fourth internal latch transistor may have a first terminal connectedto the inverted output node, a gate connected to the output node, and asecond terminal connected to the internal latch node. The internal latchnode may receive an internal latch circuit driving pulse for driving theinternal latch circuit.

The external latch circuit may comprise an equalization transistor, afirst transmission unit, a second transmission unit, and a latch unit.The equalization transistor may connect the output node to the invertedoutput node or cut off the output node from the inverted output node inresponse to an equalizing pulse. The first transmission unit may latchthe data output from the output node or output the data through a firsttransmission node in response to a data control pulse.

The second transmission unit may latch the inverted data output from theinverted output node or output the inverted data through a secondtransmission node in response to the data control pulse. The latch unitmay be connected between the first transmission node and the secondtransmission node, and store the data and the inverted data respectivelyoutput from the first transmission unit and the second transmissionunit.

The first transmission unit may invert the data output from the outputnode and transmit the inverted data to the first transmission node ifthe data control pulse is at a first level, and float the firsttransmission node if the data control pulse is at a second level. Thesecond transmission unit may invert the inverted data output from theinverted output node and transmit the inverted data to the secondtransmission node if the data control pulse is at the first level, andfloat the second transmission node if the data control pulse is at thesecond level. If the equalizing pulse is activated at the same time whenthe amplifier circuit driving pulse is activated, the amplifier circuitmay amplify the data, and if the internal latch circuit driving pulse isactivated, the equalizing pulse may be inactivated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present disclosure will become moreapparent by describing in detail exemplary embodiments thereof withreference to the attached drawings in which:

FIG. 1 is a diagram for explaining a reduction in a swing range of anexternal input signal and variations in a delay time;

FIG. 2 is a circuit diagram of a conventional amplifier circuit;

FIG. 3A is a graph illustrating an external input signal and an externalreference signal input to the conventional amplifier circuit shown inFIG. 2;

FIG. 3B is a graph illustrating data output from the conventionalamplifier circuit shown in FIG. 2;

FIG. 4 is a circuit diagram of an amplifier circuit according to anexemplary embodiment of the present disclosure;

FIG. 5A is a graph illustrating an external input signal and an externalreference signal input to the amplifier circuit shown in FIG. 4;

FIG. 5B is a graph illustrating data output from the amplifier circuitshown in FIG. 4;

FIG. 6 is a circuit diagram of a circuit for receiving data according toan exemplary embodiment of the present disclosure;

FIG. 7 is a circuit diagram of a pulse generating circuit for generatinga driving pulse in the data receiving circuit shown in FIG. 6; and

FIG. 8 is a timing diagram for explaining the operation of the datareceiving circuit shown in FIG. 6.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present disclosure will now be described more fullywith reference to the accompanying drawings, in which preferredembodiments of the disclosure are shown. In the drawings, whenever thesame element appears in a subsequent drawing, it may be denoted by thesame reference numeral.

FIG. 4 is a circuit diagram of an amplifier circuit according to anexemplary embodiment of the present disclosure. Referring to FIG. 4, anamplifier circuit 400 includes a first bias unit 410, a second bias unit420, a comparison unit 430, and an amplifier unit 440.

The first bias unit 410 responds to an internal reference signal IVREFwith a predetermined voltage level and maintains constant the amount ofa first current I1. The second bias unit 420 receives an externalreference signal XVREF, responds to a control signal CTRLV, and controlsthe amount of a second current I2 to be the same as the amount of thefirst current I1.

The comparison unit 430 compares a voltage level of a first node N1 witha voltage level of a second node N2, and controls a voltage level of thecontrol voltage CTRLV according to the comparison result. The amplifierunit 440 compares a voltage level of an external input signal XIN with avoltage level of the external reference signal XVREF, amplifies andoutputs a voltage difference between the two compared signals, respondsto the control signal CTRLV, and controls the amount of a third currentI3 to be the same as the amount of the first current I1 even though thelevel of the external reference signal XVREF is varied.

The operation of the amplifier circuit 400 according to the presentembodiment will be explained in detail with reference to FIG. 4. Thefirst bias unit 410 includes first through third bias transistors BTR1,BTR2, and BTR3.

The first bias transistor BTR1 has a first terminal connected to a powervoltage VDD, a gate connected to a ground voltage VSS, and a secondterminal connected to the first node N1. The first bias transistor BTR1is a P-channel metal oxide semiconductor (PMOS) transistor. Accordingly,the first bias transistor BTR1 is always turned on.

The second bias transistor BTR2 has a first terminal connected to thefirst node N1, and a gate to which the internal reference signal IVREFis applied. The third bias transistor BTR3 has a first terminalconnected to a second terminal of the second bias transistor BTR2, agate to which the internal reference signal IVREF is applied, and asecond terminal connected to the ground voltage VSS.

The second and third bias transistors BTR2 and BTR3 are N-channel metaloxide semiconductor (NMOS) transistors. The first current I1 flowsthrough the first through third bias transistors BTR1, BTR2, and BTR3.

The internal reference signal IVREF makes the second bias transistorBTR2 and the third bias transistor BTR3 turned on to maintain constantthe amount of the first current I1. That is, if a voltage level of theinternal reference signal IVREF is maintained constant, the amount ofthe first current I1 is maintained constant. Accordingly, the voltagelevel of the first node N1 is maintained constant.

The first bias unit 410 is a half circuit of the amplifier unit 440 thatwill be explained later, in that the size of the first bias transistorBTR1 is equal to that of a first transistor TR1 of the amplifier unit440, and the size of the second bias transistor BTR2 is equal to that ofa second transistor TR2 of the amplifier unit 440.

The second bias unit 420 includes fourth through sixth bias transistorsBTR4, BTR5, and BTR6. The fourth bias transistor BTR4 has a firstterminal connected to the power voltage VDD, a gate connected to theground voltage VSS, and a second terminal connected to the second nodeN2. The second bias transistor BTR2 is a PMOS transistor. Accordingly,the second bias transistor BTR2 is always turned on.

The fifth bias transistor BTR5 has a first terminal connected to thesecond node N2, and a gate to which the external reference signal XVREFis applied. The sixth bias transistor BTR6 has a first terminalconnected to a second terminal of the fifth bias transistor BTR5, a gateto which the control voltage CTRLV is applied, and a second terminalconnected to the ground voltage VSS.

The control voltage CTRLV controls a degree to which the sixth biastransistor BTR6 is turned on, and controls the amount of the secondcurrent I2 to be the same as the amount of the first current I1. Thatis, if the voltage level of the external reference signal XVREF input tothe fifth bias transistor BTR5 increases, the amount of the secondcurrent I2 flowing through the fifth bias transistor BTR5 increases.

Then, the control voltage CTRLV reduces the degree to which the sixthbias transistor BTR6 is turned on to reduce the amount of the secondcurrent I2. In this manner, the control voltage CTRLV controls theamount of the second current I2 to be the same as the amount of thefirst current I1.

The second bias unit 420 is a half circuit of the amplifier unit 440 inthat the size of the fourth bias transistor BTR4 is equal to that of thefirst transistor TR1 of the amplifier unit 440, and the size of thefifth bias transistor BTR5 is equal to that of the second transistor TR2of the amplifier unit 440.

The comparison unit 430 is a comparator. The comparator 430 has anegative terminal connected to the first node N1 and a positive terminalconnected to the second node N2, and reduces the voltage level of thecontrol voltage CTRLV if a voltage level of the second node N2 is higherthan the voltage level of the first node N1.

To the contrary, the comparator 430 increases the voltage level of thecontrol voltage CTRLV if the voltage level of the second node N2 islower than the voltage level of the first node N1. The fact that thevoltage level of the second node N2 is lower than the voltage level ofthe first node N1 means that the amount of the second current 12 islarger than the amount of the first current I1.

Then, the comparator 430 reduces the voltage level of the controlvoltage CTRLV to reduce the degree to which the sixth bias transistorBTR6 is turned on. Consequently, the amount of the second current I2 isreduced and the voltage level of the second node N2 increases, such thatthe voltage level of the second node N2 is maintained to be the same asthe voltage level of the first node N1. The comparator 430 compares thevoltage level of the first node N1 with the voltage level of the secondnode N2 and controls both the voltage levels to be the same.

The amplifier unit 440 includes first through fifth transistors TR1,TR2, TR3, TR4, and TR5. The first transistor TR1 has a first terminalconnected to the power voltage VDD, a gate connected to the groundvoltage VSS, and a second terminal connected to an output node OUTN. Thefirst transistor TR1 is a PMOS transistor. Accordingly, the firsttransistor TR1 is always turned on.

The second transistor TR2 has a first terminal connected to the outputnode OUTN, a gate to which the external reference signal XVREF isapplied, and a second terminal connected to a third node N3. The secondtransistor TR2 is an NMOS transistor.

The third transistor TR3 has a first terminal connected to the powervoltage VDD, a gate connected to the ground voltage VSS, and a secondterminal connected to an inverted output node OUTNB. The thirdtransistor TR3 is a PMOS transistor. Accordingly, the third transistorTR3 is always turned on.

The fourth transistor TR4 has a first terminal connected to the invertedoutput node OUTNB, a gate to which the external input signal XIN isapplied, and a second terminal connected to the third node N3. Thefourth transistor TR4 is an NMOS transistor.

The fifth transistor TR5 has a first terminal connected to the thirdnode N3, a gate to which the control voltage CTRLV is applied, and asecond terminal connected to the ground voltage VSS. The fifthtransistor TR5 is an NMOS transistor.

When the level of the external reference signal XVREF or the level ofthe external input signal XIN is varied, swing ranges and output delaytimes of data DATA and inverted data DATAB of the amplifier circuit 400are prevented from varying by using the first and second bias units 410and 420.

The size of the fifth transistor TR5 is twice that of the sixth biastransistor BTR6. The first bias unit 410 and the second bias unit 420are respectively half circuits of the amplifier unit 440, as describedabove.

The first bias unit 410 maintains constant the amount of the firstcurrent I1, and the second bias unit 420 responds to the control voltageCTRLV and maintains the amount of the second current I2 to be the sameas the amount of the first current I1 although the voltage level of theexternal reference signal XVREF is varied.

Since the external reference signal XVREF is input to both the fifthbias transistor BTR5 of the second bias unit 420 and the secondtransistor TR2 of the amplifier unit 440, level variations of theexternal reference signal XVREF affect equally the second bias unit 420and the amplifier unit 440.

The control voltage CTRLV maintains constant the amount of the secondcurrent I2 although the voltage level of the external reference signalXVREF is varied. The control voltage CTRLV is applied to the gate of thefifth transistor TR5 of the amplifier unit 440, which maintains constantthe amount of the third current I3 even though the voltage level of theexternal reference signal XVREF is varied.

That is, no matter whether the voltage level of the external referencesignal XVREF is varied, constant current determined by the first biasunit 410 flows through the amplifier unit 440. Accordingly, theamplifier unit 440 has a stable delay time and a constant output swingrange irrespective of variations in the voltage level of the externalreference signal XVREF.

For example, if the voltage level of the external reference signal XVREFincreases, a degree to which the second transistor TR2 is turned onincreases, and the amount of the third current I3 increases. Asdescribed previously, the voltage level of the control voltage CTRLVoutput from the comparison unit 430 is reduced and a degree to which thefifth transistor TR5 is turned on is reduced. Then, the amount of thethird current I3 is reduced, and finally, the amount of the thirdcurrent I3 is maintained constant and the amplifier unit 440 has aconstant delay time and a constant output swing range.

FIG. 5A is a graph illustrating the external reference signal and theexternal input signal input to the amplifier circuit shown in FIG. 4.FIG. 5B is a graph illustrating the data output from the amplifiercircuit shown in FIG. 4.

Referring to FIG. 5A, the graph 500 shows that the level of the externalinput signal XIN and the level of the external reference signal XVREFare not constant but are varied. That is, when the level of the externalinput signal XIN is varied, the level of the external reference signalis varied to 0.55V, 0.75V, and 0.95V.

In this case, the conventional amplifier circuit 220 of FIG. 2 maysuffer problems of inconstant swing ranges of data DATA and inverteddata DATAB output therefrom and long output delay times.

However, referring to FIG. 5B, the graph 550 shows that a swing range iof the data DATA output from the amplifier unit 440 of the presentdisclosure is maintained constant. Further, an output delay time TD isshorter than an output delay time TD shown in FIG. 3B.

FIG. 6 is a circuit diagram of a circuit for receiving data according toan exemplary embodiment of the present disclosure. Referring to FIG. 6,a circuit 600 for receiving data includes an amplifier circuit 610, aninternal latch circuit 620, and an external latch circuit 630.

The amplifier circuit 610 compares a voltage level of an external inputsignal XIN and a voltage level of an external reference signal XVREF,amplifies and outputs a voltage difference between the two comparedsignals, responds to a control voltage CTRLV, and maintains constant aswing range of output data.

The internal latch circuit 620 stores and amplifies the data output fromthe amplifier circuit 610. The external latch circuit 630 stores oroutwardly outputs the data output from the internal latch circuit 620.

FIG. 7 is a circuit diagram of a pulse generating circuit, which isindicated generally by the reference numeral 700, for generating adriving pulse in the data receiving circuit shown in FIG. 6.

FIG. 8 is a timing diagram, which is indicated generally by thereference numeral 800, for explaining the operation of the datareceiving circuit shown in FIG. 6.

The operation of the data receiving circuit according to the presentembodiment will be explained in detail with reference to FIGS. 6, 7 and8.

An amplifier includes a first bias unit (not shown), a second bias unit(not shown), a comparison unit (not shown), and an amplifier circuit610.

The structure and operation of the amplifier is the same as that of theamplifier circuit 400 shown in FIG. 4. For convenience of description ofthe amplifier circuit 610 shown in FIG. 6, the first bias unit, thesecond bias unit, and the comparison unit are not illustrated but onlythe amplifier unit is illustrated.

The first bias unit, the second bias unit, and the comparison unit areidentical in structure and operation to the first bias unit 410, thesecond bias unit 420, and the comparison unit 430 of the amplifiercircuit 400 shown in FIG. 4, and accordingly, a detailed explanationthereof will not be given.

The amplifier unit of the amplifier circuit 610 compares the voltagelevels of the external input signal XIN and the external referencesignal XVREF, amplifies and outputs the voltage difference between thetwo compared signals, responds to the control voltage CTRLV, andmaintains constant the swing range of the output data although thelevels of the external reference signal XVREF and the external inputsignal XIN are varied.

That is, the amplifier circuit 610 maintains constant the swing rangesof the output data DATA and DATAB although the voltage level of theexternal input signal XIN or the external reference signal XVREF isvaried as described above about the amplifier circuit 400 shown in FIG.4. The amplifier circuit 610 is turned on or off in response to apredetermined amplifier circuit driving pulse KOB.

The internal latch circuit 620 includes first through fourth internallatch transistors LTR1, LTR2, LTR3 and LTR4. The first internal latchtransistor LTR1 has a first terminal connected to a power voltage VDD, agate connected to an inverted output node OUTNB of the amplifier circuit610, and a second terminal connected to an output node OUTN of theamplifier circuit 610.

The second internal latch transistor LTR2 has a first terminal connectedto the power voltage VDD, a gate connected to the output node OUTN ofthe amplifier circuit 610, and a second terminal connected to theinverted output node OUTNB of the amplifier circuit 610.

The third internal latch transistor LTR3 has a first terminal connectedto the output node OUTN, a gate connected to the inverted output nodeOUTNB, and a second terminal connected to an internal latch node LN. Thefourth internal latch transistor LTR4 has a first terminal connected tothe inverted output node OUTNB, a gate connected to the output nodeOUTN, and a second terminal connected to the internal latch node LN. Theinternal latch node LN receives an internal latch circuit driving pulseKSPB for driving the internal latch circuit 620.

Referring to FIGS. 7 and 8, pulses for driving the data receivingcircuit 600 shown in FIG. 6 are generated from a driving pulse KB. Ifthe driving pulse KB is activated to a low level, a pulse KPATH forturning on sixth and seventh transistors TR6 and TR7 of the amplifiercircuit 610 changes to a high level as shown in position (i). In orderto separate the external latch circuit 630 from the amplifier circuit610 and the internal latch circuit 620, an equalizing pulse KSPP changesfrom a low level to a high level as shown in position (ii). Theequalizing pulse KSPP will be explained later.

If the equalizing pulse KSPP changes to a high level, the amplifiercircuit driving pulse KOB changes to a low level to drive the amplifiercircuit 610 as shown in position (iii). At this time, the internal latchcircuit driving pulse KSPB for driving the internal latch circuit 620 ismaintained at a high level, and a pulse KSP for turning on first andthird transistors TR1 and TR3 is maintained at a low level. While theinternal latch circuit driving pulse KSPB is maintained at the highlevel, the internal latch circuit 620 does not operate.

If the amplifier circuit driving pulse KOB changes to the low level, theamplifier circuit 610 amplifies a difference between the external inputsignal XIN and the external reference signal XVREF and outputs theresults to the output node OUTN and the inverted output node OUTNB.

Since the similar operation of the amplifier 610 has already beenexplained with reference to the amplifier 400 of FIG. 4, a detailedexplanation thereof will not be given. The amplifier circuit 610continues to operate until the internal latch circuit driving pulse KSPBchanges to a low level as shown in position (iv). The difference betweenthe external input signal XIN and the external reference signal XVREF isamplified slightly during a time (1) shown in FIG. 8.

Since the internal latch circuit driving pulse KSPB is maintained at thehigh level while the amplifier circuit 610 operates, the amplifiercircuit 610 responds sensitively to a very small difference between theexternal input signal XIN and the external reference signal XVREF, andis insensitive to an offset of the internal latch circuit 620.

If the internal latch circuit driving pulse KSPB changes to a low levelas shown in position (iv), the amplifier circuit driving pulse KOBchanges to a high level to turn off the amplifier circuit 610, the firstand third transistors TR1 and TR3 are turned off due to the pulse KSP,and the sixth and seventh transistors TR6 and TR7 are turned off due tothe pulse KPATH.

If the internal latch circuit driving pulse KSPB changes to the lowlevel, the internal latch circuit 620 operates and the data DATA and theinverted data DATAB respectively output from the output node OUTN andthe inverted output node OUTNB are further amplified. The data DATA andthe inverted data DATAB are amplified during a time (2) shown in FIG. 2nearly to a complementary metal oxide semiconductor (CMOS) level due tothe internal latch circuit 620.

The data DATA and the inverted data DATAB amplified by the internallatch circuit 620 are applied to first and second transmission units 631and 633. After a data control pulse KSP2 changes to a high level asshown in position (v), the equalizing pulse KSPP changes to a low levelto separate the internal latch circuit 620 from the external latchcircuit 630.

The external latch circuit 630 includes an equalization transistor ETR,the first transmission unit 631, the second transmission unit 633, and alatch unit 635. The equalization transistor ETR connects the output nodeOUTN to the inverted output node OUTNB or cuts off the output node OUTNfrom the inverted output node OUTNB in response to the equalizing pulseKSPP. While the equalizing pulse KSPP is at the low level, the internallatch circuit 620 is separated from the external latch circuit 630, andif the equalizing pulse KSPP changes to a high level, the data DATA andthe inverted data DATAB are transmitted from the internal latch circuit620 to the external latch circuit 630.

The first transmission unit 631 latches the data DATA output from theoutput node OUTN or outputs the data DATA through a first transmissionnode NTM1 in response to the data control pulse KSP2. The secondtransmission unit 633 latches the inverted data DATAB output from theinverted output node OUTNB or outputs the inverted data DATAB through asecond transmission node NTM2 in response to the data control pulseKSP2.

The latch unit 635 is connected between the first transmission node NTM1and the second transmission node NTM2, and stores the data DATA and theinverted data DATAB respectively output from the first transmission unit631 and the second transmission unit 633.

The first transmission unit 631 inverts the data DATA output from theoutput node OUTN and transmits the inverted data to the firsttransmission node NTM1 if the data control pulse KSP2 is at a firstlevel, and the first transmission unit 631 floats the first transmissionnode NTM1 if the data control pulse KSP2 is at a second level.

The second transmission unit 633 inverts the inverted data DATAB outputfrom the inverted output node OUTNB and transmits the inverted data tothe second transmission node NTM2 if the data control pulse KSP2 is atthe first level, and the second transmission unit 633 floats the secondtransmission node NTM2 if the data control pulse KSP2 is at the secondlevel.

Referring to the first transmission unit 631 shown in FIG. 6, when thedata control pulse KSP 2 is at the first level, that is, high level, thedata control pulse KSP2 is transmitted to a transistor TTR3, and aninverter INV3 inverts the data control pulse KSP2 and transmits theinverted data to a transistor TTR2.

Accordingly, the transistor TTR3 is turned on and the transistor TT2 isalso turned on. Then, the first transmission unit 631 acts as aninverter due to a transistor TTR1 and a transistor TTR4, and inverts thedata DATA and transmits the inverted data to the first transmission nodeNTM1.

If the data control pulse KSP2 is at the second level, that is, lowlevel, the transistors TTR2 and TTR3 are turned off and the firsttransmission node NTM1 is floated. If the first transmission node NTM1and the second transmission node NTM2 are floated, the data DATA and theinverted data DATAB are stored in the latch unit 635 that includesinverters INV1 and INV2. The operation of the second transmission unit633 works like the described operation of the first transmission unit631, but with the signal DATAB rather than the signal DATA.

The data DATA and the inverted data DATAB are stored in the externallatch unit 635 or output through the first and second transmission nodesNTM1 and NTM2 during a time (3) shown in FIG. 8. The data receivingcircuit 600 shown in FIG. 6 can have a constant output swing range byemploying the amplifier circuit 400 shown in FIG. 4, and can reducetotal current consumption by reducing the time (1), that is, operatingtime of the amplifier circuit 610, shown in FIG. 8.

As described above, the amplifier circuit and the data receiving circuitembodiments according to the present disclosure have an advantage ofmaintaining a constant output swing range and a stable delay timeirrespective of variations in the voltage level of the external inputsignal or the external reference signal.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the pertinent art that various changes inform and details may be made therein without departing from the spiritand scope of the present invention as defined by the following claims.

1. An amplifier circuit comprising: a first bias unit, which responds toan internal reference signal with a predetermined voltage level andmaintains constant the amount of a first current; a second bias unit,which receives an external reference signal, responds to a controlvoltage, and controls the amount of a second current to be same as theamount of the first current; a comparison unit, which compares a voltagelevel of a first node of the first bias unit with a voltage level of asecond node of the second bias unit and controls a voltage level of thecontrol voltage according to the comparison result; and an amplifierunit, which compares a voltage level of an external input signal and avoltage level of the external reference signal, amplifies and outputs avoltage difference between the external input signal and the externalreference signal, responds to the control voltage, and controls theamount of a third current to be same as the amount of the first currentalthough the level of the external reference signal is varied.
 2. Theamplifier circuit of claim 1, wherein the first current flows throughthe first node, the second current flows through the second node, andthe amount of the second current is varied in response to the voltagelevel of the external reference signal.
 3. The amplifier circuit ofclaim 1, wherein the first bias unit comprises: a first bias transistor,which has a first terminal connected to a power voltage, a gateconnected to a ground voltage, and a second terminal connected to thefirst node; a second bias transistor, which has a first terminalconnected to the first node, and a gate to which the internal referencesignal is applied; and a third bias transistor, which has a firstterminal connected to a second terminal of the second bias transistor, agate to which the internal reference signal is applied, and a secondterminal connected to the ground voltage.
 4. The amplifier circuit ofclaim 3, wherein the internal reference signal makes the second biastransistor and the third bias transistor turned on to maintain constantthe amount of the first current.
 5. The amplifier circuit of claim 1,wherein the second bias unit comprises: a fourth bias transistor, whichhas a first terminal connected to a power voltage, a gate connected to aground voltage, and a second terminal connected to the second node; afifth bias transistor, which has a first terminal connected to thesecond node, and a gate to which the external reference signal isapplied; and a sixth bias transistor, which has a first terminalconnected to a second terminal of the fifth bias transistor, a gate towhich the control voltage is applied, and a second terminal connected tothe ground voltage.
 6. The amplifier circuit of claim 5, wherein thecontrol voltage controls a degree to which the sixth bias transistor isturned on and controls the amount of the second current to be the sameas the amount of the first current.
 7. The amplifier circuit of claim 5,wherein the comparison unit has a negative terminal connected to thefirst node and a positive terminal connected to the second node, andreduces the voltage level of the control voltage if the voltage level ofthe second node is higher than the voltage level of the first node andincreases the voltage level of the control voltage if the voltage levelof the second node is lower than the voltage level of the first node. 8.The amplifier circuit of claim 5, wherein the amplifier unit comprises:a first transistor, which has a first terminal connected to the powervoltage, a gate to which a ground voltage is connected, and a secondterminal connected to an output node; a second transistor, which has afirst terminal connected to the output node, a gate to which theexternal reference signal is applied, and a second terminal connected toa third node; a third transistor, which has a first terminal connectedto the power voltage, a gate connected to the ground voltage, and asecond terminal connected to an inverted output node; a fourthtransistor, which has a first terminal connected to the inverted outputnode, a gate to which the external input signal is applied, and a secondterminal connected to the third node; and a fifth transistor, which hasa first terminal connected to the third node, a gate to which thecontrol voltage is applied, and a second terminal connected to theground voltage.
 9. The amplifier circuit of claim 8, wherein the size ofthe fifth transistor is twice that of the sixth bias transistor.
 10. Acircuit comprising: a first bias unit responsive to an internalreference signal with a predetermined voltage level for maintaining afirst current substantially constant; a second bias unit in signalcommunication with the first bias unit, responsive to a control voltagefor receiving an external reference signal and controlling a secondcurrent to be substantially the same amount as the first current; acomparison unit in signal communication with the first and second biasunits for comparing a voltage level of a first node of the first biasunit with a voltage level of a second node of the second bias unit andcontrolling a voltage level of the control voltage according to thecomparison result; and an amplifier unit in signal communication withthe comparison unit responsive to the control voltage for comparing avoltage level of an external input signal and a voltage level of theexternal reference signal, amplifying and outputting a voltagedifference between the external input signal and the external referencesignal and controlling a third current to be same as the amount of thefirst current even though the level of the external reference signal isvaried.
 11. The circuit as defined in claim 10, further comprising: aninternal latch circuit storing and amplifying the data output from theamplifier unit; and an external latch circuit in signal communicationwith the internal latch circuit for at least one of storing andoutputting data output from the internal latch circuit.
 12. The circuitas defined in claim 11, wherein the first bias unit comprises: a firstbias transistor having a first terminal connected to a power voltage, agate connected to a ground voltage, and a second terminal connected tothe first node; a second bias transistor having a first terminalconnected to the first node, and a gate to which the internal referencesignal is applied; and a third bias transistor having a first terminalconnected to a second terminal of the second bias transistor, a gate towhich the internal reference signal is applied, and a second terminalconnected to the ground voltage.